1. Field of the Invention
This invention relates generally to power supply devices adapted to supply power to ultrasonic vibrators and vehicle mirrors. More particularly, it relates to power supply devices for ultrasonic vibrators which are used in vehicle outside rear view mirrors to clear water drops, ice grains, frosted or condensated moistures, etc. on mirror surfaces, and vehicle mirrors using the ultrasonic vibrators as well as power supply devices.
2. Description of the Related Art
Japanese Laid Open Utility Model Publication No. 61-30552, that has been laid open to public inspection on Feb. 24, 1986, describes a vehicle mirror. FIG. 14 in the present application shows a cross section of a cleaning device for a car mirror disclosed in the aforementioned Japanese Publication No. 61-30552.
As seen in FIG. 14, a rear view mirror is arranged outside a vehicle body. A holder 92 has a glass mirror 91 fitted thereto. The holder 92 is fixed by a stay 93 to a car body. An ultrasonic vibrator 94, made of ceramics for example, is arranged between the holder 92 and the stay 93. An operation switch 95 is disposed in the cabin of the vehicle and is connected with the vibrator 94 so that the vibrator can be operated from the cabin. A drive circuit 96 and a power source 97 are connected in series to the ultrasonic vibrator 94 and the operation switch 95.
The drive circuit 96 amplifies signals, generated by an oscillator, through an amplifier and sends amplified signals to the vibrator 94 to make it vibrate accordingly.
The vehicle mirror with this ultrasonic vibrator 94 operates as follows.
When water drops are deposited on a mirror surface, the operation switch 95 is switched on to work the vibrator 94. Then, the vibrator 94 oscillates the entire holder 92 and removes the water drops on the mirror surface.
To effect such operation, it is necessary to supply power of an ultrasonic oscillation frequency to the vibrator 94 through lead wires and the like. However, vibration is also transmitted and this can apply some stress to the lead wires, thereby possibly causing breakage of the lead wires at the places where the wires are joined to the vibrator 94. Therefore, durability of the lead wires is a matter of concern in the conventional vehicle mirror.
Japanese Laid Open Utility Model Publication No. 59-40145, which has been laid open to public inspection on 1984, shows another vehicle mirror. FIG. 15 is a perspective view of a rear surface of the vehicle mirror arranged outside a car body.
As seen in FIG. 15, a planar heater 102 is fitted to the rear surface of a mirror 101. The heater 102 is supplied with power through terminals 103 and 104 to heat a front surface of the mirror 101. The water drops on the mirror surface are cleared off as the front surface of the mirror 101 is heated, so that a clear view through the mirror is possible.
The combination of the heater 102 and an ultrasonic vibrator may be available to assure a clear view through a mirror. In this case, the strength of the lead wires at the terminals 103 and 104 is also a matter of concern, since they suffer from stress by the vibrator.
The inventors of the present application have found that a flexible material such as flexible cable absorbed by itself the stress and was fatigued when used for supplying power to a vibrator. This material prevents breakage of a circuit and contributes much to prolongation of the life of the circuit.
However, the flexible material is so expensive that, it will increase the price of the mirror. Moreover, there will be trouble if the flexible material is damaged by scratches in assembling work. Therefore, much care is necessary to handle the flexible material in the assembling work, thereby making it difficult to improve the work efficiency.